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HIGH ENERGY HOSTS AND BLUE EMITTERS FOR PHOSPHORESCENT
ORGANIC LIGHT EMITTING DIODES
by
Wei Wei
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMISTRY)
December 2010
Copyright 2010 Wei Wei

Organic light emitting diodes (OLEDs) have achieved high levels of performance including high efficiencies, color purities and device lifetimes. It has been widely utilized in commercial applications except that the blue device lifetime is still poor compared to red and green devices. The stability of high energy OLED materials is a key issue to be addressed for achieving a long life and efficient blue device. In this dissertation, a great effort has been put into developing more stable and more efficient materials that can also fulfill the band gap and photophysical requirements. The materials studied include large bad gap hosts and blue phosphorescent emitters.; In chapter 2 and 3, multi-fluorenyl silanes, silyl spirobifluorenes and methyl spirobifluorenes have been studied as potential hosts for phosphorescent OLEDs. These materials have high triplet energies, large HOMO-LUMO gaps and high glass transition temperatures and they also show ambipolar transport characteristics in OLED devices. The device current could be enhanced by increasing the fluorene ratios in the hosts. These materials were also tested in phosphorescent OLEDs and have been proved to be good hosts for red, green and blue devices.; In the second part of this dissertation, studies on large band gap iridium complexes are demonstrated. These cyclometalated iridium complexes are all derivatives of iridium (III) tris(1-phenyl-pyrazole) (Ir(ppz)3). Chapter 5 is dedicated to solve an electron trapping problem of fluorenyl pyrazolyl Ir complexes. A better electron trapping group, fluorene, was incorporated into the ligand through a spiro structure. Photophysical studies and OLED fabrications were utilitzed to test these spirobifluorene based Ir cyclometalated complexes. Characterization and isomerization studies of rigid ligand heteroleptic Ir complexes will be discussed in Chapter 4. It was found that these heteroleptic complexes could isomerize during sublimation. In chapter 6, some results from temperature dependence studies will be discussed to discover the triplet deactivation of phenylpyrazole related Ir complexes.

HIGH ENERGY HOSTS AND BLUE EMITTERS FOR PHOSPHORESCENT
ORGANIC LIGHT EMITTING DIODES
by
Wei Wei
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMISTRY)
December 2010
Copyright 2010 Wei Wei